Vray and Sub Surface Scattering

For our origami crane to look as realistic as possible, we need to apply a shader that can mimic the properties of real paper.  This is one of the reasons I wanted to use V-ray to render out our assets. The capabilities of its shader set are far more advance than those of mentalray and its a far more widely used renderer in the industry, so it would be ideal to learn as soon as possible.

During our recent visit to the Bournemouth FX festival, there was a lot of talks about V-ray. At a talk from Random42; a medical animation studio, where V-ray is there main renderer; they spoke about a shader called VrayfastSSS2 or Vray Sub Surface Scattering. Its main purpose is for rendering translucent materials like skin or marble. One of the benefits for the SSS2 shader is that it allows light through a material based off of the density of the object, which is perfect for our crane model as some parts like the wings are thin and need to allow more light through than the body, which is quite dense with paper folds.

From these examples we can clearly see how light is being scattered around the object and by increasing the scale parameter we can adjust at what depth the light is scattered to giving it a more translucent effect. Although you do lose some of the definition from the lack of shadows, so there is a balancing act in finding the sweet spot.

Here is some of my experiments using the SSS2 shader on our crane model. In the first image I was having some difficulty with the V-ray subdivisions causing the shader to react oddly to  the geometry. In the second image I’ve solved the problem and increased the amount of scatter light. We can see its effect clearly on the wing along its fold line. the third and fourth images are using the same shader but the fourth image has improved UVs so the noise bump map would effect it properly. I still need to add normal map to add some finer details and to add a diffuse layer to apply a uniform texture.

vray shader.PNG

Here the settings I have at the moment. The overall colour will be changed to the diffuse channel I export from substance painter and I should change the index of refraction to closer mimic the IOR of paper, at the moment it is set to 1.3, this setting is for most water based materials.

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The Chaos group website is a fantastic source for every piece of information you could want about VRay. The documentation is very thorough and precise and easy to navigate. This source has vastly helped me improve my ability to texture/shade and render in VRay. There are even tutorials on some more general concepts of Vray.

https://docs.chaosgroup.com/display/VRAY3MAYA/Subsurface+Scattering+Material+%7C+VRayFastSSS2

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